In U.S. Pat. No. 3,961,625 issued June 8, 1976, to the present inventor, method and apparatus were disclosed and claimed whereby a treatment is provided which provides pressure pulses to a patient's leg at a time in the arterial pulse cycle to reinforce the pulse which forces blood into the leg, and which relieves the pressure at a time in the pulse cycle to enable the next pulse to enter the leg without undue obstruction. Such treatment simultaneously provides a reinforcement of the movement of blood into the leg, and provides an enhancement of the return of blood from the leg to the heart, thereby increasing the overall circulation through the leg.
In the treatment, intermittent external pressure pulses are supplied to the leg, and timed in such fashion that the pressure pulse follows close upon the arrival of the arterial pulse at the upper end of the leg being treated, and reinforces the action of the arterial pulse in forcing blood into the leg. Between the external pressure pulses, the external pressure is removed or diminished, so that upon a succeeding arterial pulse, there is little or no external pressure on the leg, and the succeeding arterial pulse may enter the leg without undue obstruction resulting from external pressure.
The pressure pulses are supplied to the entire leg, so that the pressure acts not only in a portion of the arterial system of the leg, but to enhance the flow of blood in the entire arterial system, and to aid venous return from the leg to the heart. The pressure acts over a large portion of the affected area, enhancing the flow of blood from the area toward the heart and improving the circulation in the leg over that obtained by applying external pressure only in a relatively narrow band as in the prior art.
The application of the pressure is typically set at a predetermined variable interval after the QRS complex of the electrocardiogram, and the relief of the pressure is either set at a predetermined variable interval after application of the pressure or triggered by the QRS complex itself. The pressure is relieved at the time that the heart pulse arrives at the leg, so that the pulse enters the leg without interference from external pressure. The pressure is reapplied at a subsequent time at which the pulse has substantially entirely entered the leg, so that no interference with entry of the pulse into the leg results, and the effect of the pressure is to promote movement of blood through the leg, improving the circulation.
The application of pressure is preferably gradual, as compressed gas is re-introduced into the enclosure and the pressure in the enclosure gradually increases from approximately atmospheric to, typically 1 to 2 psig. The relief of pressure is sudden, by opening a valve from the enclosure to the atmosphere. The optimum timing of the application of pressure depends on the pulse rate and on the amount of free space in the enclosure surrounding the leg. For a pulse rate of 80 (0.75 second per beat), with a relatively small amount of free space in the enclosure, so that the pressure is applied rather quickly, the pressure might typically be applied about 0.45 seconds after the QRS complex of the cardiogram and continued for 0.3 second until the next QRS complex, at which time the pressure is relieved. For a pulse rate of 40 (1.5 seconds per beat), again with relatively little free space, the pressure might typically be applied about 0.8 seconds after the QRS complex and again continued for 0.7 seconds until the next QRS complex.